In this communication era there is an increasing need for facilities to provide fast communications between end users, at the lowest possible cost for said users.
This is further emphasized by the increasing competition between carriers. Increasing use of communication facilities, has increased competition between private companies herein referred to as customer network and service provider networks (building international communication networks for offering communication services to the public). The latter shall be referred to, herein, as international service provider networks. Also, most countries are still running their own public telephone networks. Finally, these different types of networks are often interconnected, providing a multi-network facility to users throughout the world.
The situation is further compounded by the fact that in most private networks, the private companies running the networks may own node facilities, they often do not own the interconnecting lines. These lines are leased by a carrier at prices fixed (i.e., per year) no matter whether they are fully used or not. Accordingly, optimizing line bandwidth occupation is a must for the private network owner.
In the U.S., the available links include so-called T1 operating at 1.544 Mbps and T3 at 44.736 Mbps, while in Europe one may find E1 at 2.048 Mbps and E3 at 34.368 Mbps. The tariffs applied in 1995 were, in France (in K$ per month) as indicated hereunder:
______________________________________ 50 km 250 Km 500 Km ______________________________________ E1 = 2 10 14 E3 = 50 150 170 ______________________________________
The above, helps demonstrate the importance of optimizing link bandwidths for the network. Properly designed networks must include means for orienting the traffic between the network nodes to fulfill these actual optimal bandwidth occupation requirements.
On the other hand, public telephone network owners do apply their own tariffs based on several parameters including distance travelled by the user's traffic within the network (i.e., distance between network entry and exit); duration of the connection; and the time of the day or period of said traffic.
Finally, actual communications between end users (including service providers) often follow rather complex paths which might include going through several kinds of networks. For instance, assume a situation of interconnected networks as represented in FIG. 1. Two customer networks (10 and 11) are attached to a service provider network (12) which might extend internationally. The system also includes two public networks (13 and 14) each covering a different country (e.g. France and Germany). All these networks are interconnected into a multi-network facility as represented in the figure. A request issuing from end user A calling end user B may be executed to follow any one of the three paths (1), (2) or (3) represented by the dotted arrows in FIG. 1.
One issue in such an environment is to find, at said call set-up, the path which optimizes the communication cost for the end user (customer). This is the function of the so called Least Cost Routing (LCR) process. With the presently available price parameters, the LCR path, in the case of a call from A to B as represented in FIG. 1, should be achieved by selecting the path with the shortest distance within the public networks. This is due to the fact that public network tariffs are usually higher than the cost within the private networks and are a function of the path length within said network. Accordingly, path (3) should be the best one for connecting A to B, and the LCR process should operate within the private network, be it a customer or a service provider network, for selecting the best private network port and trunk(s) to achieve said LCR accordingly.
FIG. 2 shows schematically, a network (similar to the network of FIG. 1), with the presently available facilities within the service provider (private) network and the public network, for establishing a path between end users' terminals. Assuming that the end user A (telephone set) is calling telephone set C (or any service provider connected via public network) which has been assigned a telephone reference number 364000 (which reference, herein also designated as "number" can also bear an alpha-numerical form) and that terminals A and C are attached to a private network service provider including three nodes (Node 1, Node 2 and Node 3) with means for digitally encoding the voice signals. These nodes being located on a private telephone network, they include telephone switches called Private Branch eXchanges (PBX's). These PBX's allow going into intra-enterprise communication without going through public network, as well as providing access to the public telephone network.
Node 1 is attached to Node 2 via a trunk Tr1 which may be a leased line (L.L). Node 3 is attached to both Nodes 1 and 2, with the connection between Node 1 and Node 3 operating via trunk Tr0. Also represented are two public networks PN1 and PN2, with PN1 being connected to the private network via trunks Tr2 and Tr3, issuing from Node 1, while PN2 is connected to the private network via trunk Tr4 issuing from Node 2. Both public networks PN1 and PN2 are interconnected via a Trunk Tr5. The network PN2 might be a public telephone network including Central office eXchanges (CX's) of both types (i.e., access CXs concentrating telephone subscribers' (users') lines directly attached therein and transit CX's handling inter-CX's traffic at regional, national or international level).
In presently available networks, each node trunk connection down to an extension is assigned a numbered physical connection which is recorded in a routing table. For instance, Node 1 may include a routing table associating the trunk Tr1 to the table entry 36 . . . ; the trunk Tr0 to entry 21 . . . etc. . . Node2 may include a routing table associating trunk Tr4 to the entry 3640. . . In other words the routing tables are configured in a "hop by hop" manner to enable setting the path throughout the network by matching to progressively increasing portions of called user terminal address (e.g., telephone number). In addition the routing tables include several entries per destination, including: prioritized alternate routes; route selection based on circuit availability; route selection based on Time-Of-Day (TOD) according to the tariff applied for the call; etc. . . , all information required for implementing the Least Cost Routing function. All required data are manually entered into the tables in the form of so called wildcarded data and it should be understood that the required table data are lengthy to store.
Also, the private network owner may need access to a terminal attached to the public network while fulfilling Least Cost Routing requirements should not only configure his network facilities accordingly, (i.e., offering the path encompassing the shortest path through the public network, and manually enter the wilcarded data) but, should also update these data as often as required while always optimizing link bandwidths within the network.
A person of ordinary skill in the art fully appreciates a method for avoiding the hassle of the above facilities operation for providing Least Cost Routing function.